Trans-1,4-polyisoprene (TPI), which is also called synthetic Gutta percha, Gutta percha, Balata etc., is an isomer of universal natural rubber (NR) and isoprene rubber (IR). At room temperature, TPI has easy crystallinity and the melting point is merely about 60 degrees Celsius, so it can be used for medical fixed orthopedic materials and the like as a low melting point plastic. However, the TPI's molecular chain is essentially a flexible unsaturated chain containing carbon-carbon double bonds, thus it can be crosslinked by the same vulcanization method of unsaturated rubbers. If the crosslink density is lower, TPI is a thermotropic rubber elastomer, that is, it performs the elastomer feature over 60 degrees Celsius and crystallizates at room temperature, which can be used as shape memory functional materials; If the crosslink density is higher, TPI is turned into elastomer materials because crosslinking prevents crystallization. Such elastomer has advantageous characteristics as good dynamic performance, low heat-building, good fatigue tolerance, therefore it is a good material for manufacturing high performance tyres with green, energy saving and environmental conservation, and damping product of high speed trains and cars. So it can be seen that TPI is a plastic as well as a rubber, meanwhile it can be used as functional material, which is a new polymer material with a variety of applications.
Eucommia ulmoides Oliv. is a unique species in China, and the Gutta-percha can be extracted from the skin, leaves and seeds of Eucommia ulmoides. Ruifang Yan, researcher of Institute of Chemistry Chinese Academy of Sciences, has made a great deal of work on the development of Gutta-percha; the Gutta-percha which is also called Balata etc. has also been extracted from related plants. Because the contents are limited, and the extraction method is complicated, so the cost and price are high, and the applications are badly restricted.
The earliest patent for TPI synthesis was published in 1955 (British Patent Publication No. 834554 and Italian Patent Publication IT553904). From 1960s, Canada Polysar, UK Dunlop, Japan Kurary etc. successively built industrial devices for TPI synthesis, which are all small devices around several hundreds tons yearly. These devices all adopt a process of solution polymerization catalyzed by Vanadium catalyst system or Vanadium-Titanium mixed catalyst system, which is similar to the process of polybutadiene rubber. Due to the low catalysis activity (only 1-2 kg TPI/gV), complicated process, high energy and material consumption, small production scale, the cost of production is high. At present, the international market price of TPI is USD35/Kg, which is more than ten times higher than that of the ordinary rubber materials, thus very limits the market development of TPI to only special applications like medical materials etc. It is said that only a Japanese company is still producing TPI currently, which model is TP-301.